Burner arrangement



July 9, 1968' A. J. HOARE 3,

BURNER ARRANGEMENT Filed Sept. 29, 1966 s Sheets-Sheet 1 k ----70 mmJuly 9,1968 A, J. HOARE 3,391,675

BURNER ARRANGEMENT I xxxxxxxx oooooooo XXXXXXXX 00000099 July 9, 1968 A.J; HOARE 3,39

BURNER ARRANGEMENT Filed Sept. 29, 1966 s Sheets-Sheet s United StatesPatent 3,391,675 BURNER ARRANGEMENT Anthony J. Hoare, Ascot, England,assignor to Foster Wheeler Corporation, Livingston, N.J., a corporationof New York Filed Sept. 29, 1966, Ser. No. 583,034

Claims priority, application Great Britain, Sept. 29, 1965,

1 Claim. (Cl. 122-235) ABSTRACT OF THE DISCLOSURE A burner arrangementfor a vapor generator in which the burners are arranged in rows on thefront wall that are vertically displaced from the rows of burners whichare mounted on the rear wall. The rear wall is formed with an extendingnose projection, and the horizontal row of burners which is mostupwardly disposed in the furnace chamber is located on the rear wallsuch that the hot combusted gases are biased away from the rear wall forflow around the projection.

It is usual for such furnaces to be of rectangular cross section and forthe burners to be set in one of the walls. It happens sometimes,however, that the burners need to be set in a pair of opposite walls toimprove the heat flux distribution around the furnace and it has beenfound that, if the burners are placed exactly opposite each other, thegas flow becomes concentrated in the centre band of the furnace whichresults in poor gas distribution at furnace outlet and inefficient heattransfer.

Also, it has been noticed that when there are two rows of axiallyopposed burners there is a tendency for the gases from one of the twoopposed burners at each end of its row to be offset outside the gasesfrom the other burner at the end of the row; this could result in flameimpingement or overheating of the side or division walls in the furnace.

According to the invention, there is provided a furnace having opposingwalls in each of which are positioned one or more substantiallyhorizontal rows of burners which are fixed in orientation and aresubstantially normal to the wall in which they are positioned and pointto the opposing wall, the rows of burners in opposing walls beingvertically staggered so that there is no axial alignment between burnersof opposing walls.

Furnaces made this way have been found to give much more evendistribution of the hot gases over the cross section of the furnace andat the entry to convective regions of a boiler associated with thefurnace.

It is preferred that a row of burners in one opposing wall be higher orlower than the adjacent row of burners in the opposite wall by adistance equal to at least half the normal spacing between theindividual burners in each row.

The side wall in which the highest row of burners is positioned can bechosen with advantage to bias the flow of gases in the furnace outlet sothat they will flow most evenly around the bend between the furnaceoutlet and the connective regions of a boiler associated with thefurnace.

The invention is particularly useful in larger boilers of theonce-through or natural circulation water tube types in which the steamgenerating and other processing tubes are disposed in a shell risingvertically from a furnace.

The invention will now be described, by way of example, with referenceto the accompanying diagrammatic drawings, in which:

FIGURE 1 is a vertical section through a steam boiler 3,391,675 PatentedJuly 9, 1968 incorporating a furnace not in accordance with theinventlon;

'FIGURE 2 is a section on line 2--2 of FIGURE 1;

FIGURE 3 is a vertical section similar to FIGURE 1 of a steam boilerincorporating a furnace in accordance with the invention;

3 FIGURE 4 is a section on the line 4-4 of FIGURE and FIGURE 5 is adiagram illustraitng a furnace in accordance with the invention.

The steam boiler 10 shown in FIGURE 1 has a furnace 11 which leads to asteam generating region 12 and both the furnace and this region arelined with steam generating water tubes 14. Near the top of the region12 some of the water tubes lining the rear wall 16 are bent outwardly toform a nose 17, although this is not essential. The combustion gasesfrom the furnace then pass over a superheater 18, reheater 20 andeconomiser 22 before passing to a stack (not shown). They may also passover an air heater if desired.

At the base of the furnace there is 'a region 24 for ash collection.

The front and rear walls 26 and 16 of the furnace are provided withburners 28 which are arranged in horizontal rows of four burners per row(FIGURE 2), and there are three vertically spaced rows in each wall. Ascan be seen in FIGURE 1, the conventional furnace has the rows ofburners in the opposite sides on substantially the same level and theflames from opposite pairs of aligned burners impinge against oneanother at around the middle of the furnace.

This arrangement does not give particularly thorough mixing of thecombustion gases and give a bad flow distribution of the combustionproducts over the crosssection of the furnace 11 and steam generatingsection 12, that is to say the combustion products tends to pass up themiddle of the furnace and steam generating section as shown by the fiowlines 30 and do not therefore heat the tubes 14 evenly.

Another disadvantage of the arrangement is, as shown in FIGURE 2, thatthe flames 32 from burners at the ends of a row are liable to be offsetoutside the flame from the opposite burners and then there is a veryserious risk of the flame impinging on the side wall 34 of the furnacein the region 36 so as to overheat the water tubes in that region.

In accordance with the invention these difficulties are overcome in thefurnace 40 shown in FIGURES 3 and 4 by staggering the rows of burners inthe front and rear walls so that no two burners are in axial alignment.

In the arrangement shown the highest row of burners is in the rear wall,but this is not essential. The arrangement shown is preferred, however,since this gives a degree of bias to the upward travel of the combustionproducts which assists their travel around the bend above the nose 17.

The staggering of the rows of burners leads to considerable turbulanceand mixing of the flames from the various burners and a more completecombustion. Also the combustion products are, as shown by the flow lines42 in FIGURE 3, far more evenly distributed over the cross section ofthe furnace 40 and steam generating section 12, and as shown in FIGURE4, there is far less chance of the flames 32 impinging on the side walls34 and causing overheating of some of the water tubes.

FIGURE 5 is a diagram showing the relative positions of the burners 28in the furnace and X represents the position of a burner in the rearwall 16, 0 the position of a burner in the front wall 26, and the brokenlines the side walls 34 of the furnace. With the staggering of the rowsof burners it is preferred that a row of burners in one wall be higheror lower than the adjacent row in the opposite wall by a distance equalto at least half the normal spacing between the individual burners ineach row, i.e. as shown in FIGURE 5, x should be greater than y/ 2.

The drawings show three rows of burners in each wall with four burnersper row, these numbers are, however, in no way critical.

I claim:

1. A vapor generator comprising front and rear walls defining an uprightfurnace chamber and a steam generating section above and aligned withsaid furnace chamber for receiving hot combusted gases from said furnacechamber, a horizontal convection 'area extending rearwardly from theupper part of said generating section receiving gases from thegenerating section, means for supplying feedwater to said generatingsection for producing steam, said rear wall being bent towards saidfront wall in said vapor generating section to form a nose projectionextending over said furnace section, a plurality of burners mounted onsaid front and rear walls in spaced apart confronting horizontal rows,the rows of burners which are mounted on the front wall being displacedvertically from the rows of burners which are mounted on the rear wall,said furnace section being open to the extent that the burners on onewall are exposed to the burners on the other Wall, the horizontal row ofburners which is most upwardly disposed in said furnace chamber withrespect to said generating section being located on said rear wall suchthat said hot combusted gases are biased away from said rear wall forflow around said nose projection.

References Cited UNITED STATES PATENTS 2,807,242 9/1957 Poole. 3,202,1968/1965 Rackley et a1. 3,254,635 6/1966 Schoppe 122-356 XR KENNETH W.SPRAGUE, Primary Examiner.

